In commonly assigned U.S. Pat. Nos. 4,965,626 and 5,229,810, a photographic filmstrip having a virtually transparent, magnetic film layer on the non-emulsion side of the filmstrip (referred to as an MOF layer) is disclosed for use in camera systems. One or more longitudinal read/write tracks are illustrated in the MOF layer between the side edges of the image frame area and the filmstrip where information such as film type, film speed, film exposure information and information relevant to the processing and subsequent use (e.g., printing) of the exposed image frames is pre-recorded during manufacture of the filmstrip cartridge. The pre-recorded information useful for controlling camera operations may be read out in a camera, and information related to the exposure of an image frame may be recorded in certain other tracks during camera use. The information recorded during camera use may include voice messages or sound associated with the photographed scene and may be recorded in digital or analog format on the certain tracks. It is contemplated that both the pre-recorded and the camera use recorded information will be read out for control and reprint purposes during photofinishing. Also, it is contemplated that the photofinisher may have the capability to record additional information related to finishing, e.g. printing exposure conditions, customer information, reorder information, etc., in further tracks.
Although, the recording of information in the image frame area tracks of the MOF layer has been proposed in the '626 and '810 patents, and elsewhere, camera systems for magnetic reproducing and recording in the MOF layer have largely been devoted to recording and reproducing in the edge tracks and filmstrip leader. The difficulty in providing the high, optimal degree of compliance with the optically transparent, low magnetic particle concentration, MOF layer, without causing optically visible damage to the filmstrip emulsion layers or MOF layer, is perceived as a deterrent.
The MOF layer is optically transparent and is formed of low concentration magnetic particles. The low concentration requires the optimal head gap compliance with the MOF layer and also limits the digital data recording density. The digitized information has to be encoded in bytes as described in the above-referenced '810 and '626 patents. These limitations and requirements in turn limit the amount of information that may be recorded in each track. The number of possible magnetic heads that can be economically fabricated in the head array will also become insufficient to meet the information storage capacity needed for recording in cameras or in other equipment.